Machine-to-Machine communication is a form of data communication which involves one or more entities that do not necessarily need human interaction. Machine Type Communication (MTC) services have introduced a plurality of new features which are different from for example the services provided by current mobile network communications. For example, the MTC service has a burst characteristic and might involve a potentially large number of communicating terminals, resulting in a dramatic increase of communication connections within a short time. In the MTC service, the potentially large number of communicating terminals may attempt almost simultaneously to attach to an access network or activate a connection. For example, consider a typical application—bridge monitoring with a mass of sensors. Hundreds or even thousands of sensors may simultaneously initiate network access when a vehicle passes through the bridge. Or, consider another typical application—metering. Thousands of meters in buildings may start to report their measurements or reading results at almost the same predetermined time, say 12:00 pm (generally, a precise reporting time will not be scheduled for each meter). Apparently, such a burst of access attempts is highly possible to collide with each other in the access channels of the access network, and even collide with normal access attempts of other non-MTC devices served by the access network. This causes congestion in the access channels (e.g. random access channels) of the access network which is originally designed for the access attempts of human-to-human communications, and thus dampening, for example, normal communications between conventional user equipments, which have stricter requirements on guaranteed transmission quality. The typical common RACH (PRACH) load in 3GPP LTE is about 128 attempts per second at 10 MHz. However, the PRACH load caused by a mass of MTC devices may be far beyond this.
In addition, the present study on Machine-to-Machine communications further points out a possibility to perform MTC through a mobile network. However, in order to provide the mobile network with competitiveness in Machine Type Applications, there is a need for optimization so as to support the features of MTC.
In 3GPP LTE, a variety of available RACH time-frequency resource configurations are specified for different system bandwidths and different numbers of cells of each base station (or enhanced base station eNB). It should be understood that more RACH time-frequency resources can be configured in advance to accommodate a potential burst of MTC device access, i.e., configuring RACH video resources of a system based on the number of MTC access attempts during a burst. However, the semi-static resource configuration may waste much of uplink resources due to the burst characteristic of the MTC device access. In addition, even if the base station is configured to provide more access time-frequency resources, considering the considerable number of MTC devices and simultaneity of their access operations, the uplink resources to accommodate the burst of MTC device access may not be sufficient, especially for a system with a high system bandwidth or in a case of multiple cells under each base station. Because for such system and such case, the number of access time-frequency resources for non-MTC device access has been considerable, it would be difficult to reserve sufficient time-frequency resources for the MTC devices without affecting the access of non-MTC devices.
Therefore, there is a need for a network access method for MTC, such that even when a considerable number of MTC devices attempt to perform access simultaneously, it can still guarantee that the access of non-MTC devices is not affected. Meanwhile, the method can support such features of the MTC services as burst, a considerable number of access requests, etc., so as to dynamically assign the required access time-frequency resources according to requirements, resolve congestion in the RACH channels, and avoid waste of the uplink resources.